Zanzibar Buck-Buck McFate said:
Because teams aren't using the same mix of skaters with one less guy out there to begin with in 3/3 OT, so you've got a different set of options depending on who takes the penalty and who the opposing coach puts out there. The whole dynamic is changed.
Except that's demonstrably not true. Teams could always use whoever they wanted on a 4 on 3 powerplay in OT and they would and do always use a modified version of their regular PP or their normal 4 on 3. The killing team will use the same group of penalty killers they would in any three man situation. The options are exactly the same and it doesn't drastically alter which strategies are successful and which aren't.
More to the point that has absolutely nothing to do with the actual strategy of scoring on this particular 4 on 3 powerplay. There's nothing about using Rielly, who the team used in 4 on 4 and 3 on 3 OT situations, that is different or new or wouldn't be available to them in any other 4 on 3 situation. Phaneuf, likewise, was used in all of these situations. There's no appreciable difference in the "dynamic" of who the Leafs might have used 4 on 3.